Diarrhoeagenic Escherichia coli--an emerging problem?

Population structure and pathogen interaction of Escherichia coli in freshwater: Implications of land-use for water quality and public health in Aotearoa New Zealand

Freshwater samples (n = 199) were obtained from 41 sites with contrasting land-uses (avian, low impact, dairy, urban, sheep and beef, and mixed sheep, beef and dairy) and the E. coli phylotype of 3980 isolates (20 per water sample enrichment) was determined. Eight phylotypes were identified with B1 (48.04%), B2 (14.87%) and A (14.79%) the most abundant. Escherichia marmotae (n = 22), and Escherichia ruysiae (n = 1), were rare (0.68%) suggesting that these environmental strains are unlikely to confound water quality assessments. Phylotypes A and B1 were overrepresented in dairy and urban sites (p < 0.0001), whilst B2 were overrepresented in low impact sites (p < 0.0001). Pathogens ((Salmonella, Campylobacter, Cryptosporidium or Giardia) and the presence of diarrhoeagenic E. coli-associated genes (stx and eae) were detected in 89.9% (179/199) samples, including 80.5% (33/41) of samples with putative non-recent faecal inputs. Quantitative PCR to detect microbial source tracking targets from human, ruminant and avian contamination were concordant with land-use type and E. coli phylotype abundance. This study demonstrated that a potential recreational health risk remains where pathogens occurred in water samples with low E. coli concentration, potential non-recent faecal sources, low impact sites and where human, ruminant and avian faecal sources were absent.

ColiSeq: a multiplex amplicon assay that provides strain level resolution of Escherichia coli directly from clinical specimens

Escherichia coli is a diverse pathogen, causing a range of disease in humans, from self-limiting diarrhea to urinary tract infections (UTIs). Uropathogenic E. coli (UPEC) is the most frequently observed uropathogen in UTIs, a common disease in high-income countries, incurring billions of dollars yearly in treatment costs. Although E. coli is easily grown and identified in the clinical laboratory, genotyping the pathogen is more complicated, yet critical for reducing the incidence of disease. These goals can be achieved through whole-genome sequencing of E. coli isolates, but this approach is relatively slow and typically requires culturing the pathogen in the laboratory. To genotype E. coli rapidly and inexpensively directly from clinical samples, including but not limited to urine, we developed and validated a multiplex amplicon sequencing assay, called ColiSeq. The assay consists of targets designed for E. coli species confirmation, high resolution genotyping, and mixture deconvolution. To demonstrate its utility, we screened the ColiSeq assay against 230 clinical urine samples collected from a hospital system in Flagstaff, Arizona, USA. A limit of detection analysis demonstrated the ability of ColiSeq to identify E. coli at a concentration of ~2 genomic equivalent (GEs)/mL and to generate high-resolution genotyping at a concentration of 1 × 105 GEs/mL. The results of this study suggest that ColiSeq could be a valuable method to understand the source of UPEC strains and guide infection mitigation efforts. As sequence-based diagnostics become accepted in the clinical laboratory, workflows such as ColiSeq will provide actionable information to improve patient outcomes.IMPORTANCEUrinary tract infections (UTIs), caused primarily by Escherichia coli, create an enormous health care burden in the United States and other high-income countries. The early detection of E. coli from clinical samples, including urine, is important to target therapy and prevent further patient complications. Additionally, understanding the source of E. coli exposure will help with future mitigation efforts. In this study, we developed, tested, and validated an amplicon sequencing assay focused on direct detection of E. coli from urine. The resulting sequence data were demonstrated to provide strain level resolution of the pathogen, not only confirming the presence of E. coli, which can focus treatment efforts, but also providing data needed for source attribution and contact tracing. This assay will generate inexpensive, rapid, and reproducible data that can be deployed by public health agencies to track, diagnose, and potentially mitigate future UTIs caused by E. coli.

An Overview of Date (Phoenix dactylifera) Fruits as an Important Global Food Resource

Dates are the fruits of the date palm belonging to the Arecaceae family; they comprise over 2500 species and 200 genera and constitute an essential part of the daily diet worldwide, with beneficial nutritional, health, and economic values. Several varieties of date palm (Phoenix dactylifera) fruit exist globally, especially in hot and humid regions. This review is an overview of date palms as a significant global food resource, including their historical significance, nutritional composition, cultivation practices, economic importance, and health benefits. The historical journey of dates goes back to ancient civilizations where they were revered for their richness in essential nutrients and natural sweetness. Today, dates are a vital crop in arid regions, contributing substantially to the agricultural economy and livelihoods of communities. This paper further explores the cultivation techniques employed to enhance date production. Furthermore, the nutritional composition of dates is analyzed in detail, highlighting their high content of vitamins, minerals, dietary fibers, and antioxidants. These attributes make dates a delicious treat and a valuable nutritional component, offering numerous health benefits. The potential health effects, including improved digestion, enhanced cardiovascular health, and increased energy levels, are discussed. Additionally, this paper delves into the economic significance of the date industry and its global trade.

Lactiplantibacillus plantarum L47 and inulin alleviate enterotoxigenic Escherichia coli induced ileal inflammation in piglets by upregulating the levels of α-linolenic acid and 12,13-epoxyoctadecenoic acid

Alternatives to antibiotics for preventing bacteria-induced inflammation in early-weaned farm animals are sorely needed. Our previous study showed that Lactiplantibacillus plantarum L47 and inulin could alleviate dextran sulfate sodium (DSS)-induced colitis in mice. To explore the protective effects of L. plantarum L47 and inulin on the ileal inflammatory response in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC), 28 weaned piglets were assigned into four groups, namely, CON group-orally given 10 mL/d phosphate buffer saline (PBS), LI47 group-orally given a mixture of 10 mL/d L. plantarum L47 and inulin, ECON group-orally given 10 mL/d PBS and challenged by ETEC, and ELI47 group-orally given 10 mL/d L. plantarum L47 and inulin mixture and challenged by ETEC. The results demonstrated that the combination of L. plantarum L47 and inulin reduced inflammatory responses and relieved the inflammatory damage caused by ETEC, including ileal morphological damage, reduced protein expression of ileal tight junction, decreased antioxidant capacity, and decreased anti-inflammatory factors. Transcriptome analysis revealed that L. plantarum L47 and inulin up-regulated the gene expression of phospholipase A2 group IIA (PLA2G2A) (P < 0.05) as well as affected alpha-linolenic acid (ALA) metabolism and linoleic acid metabolism. Moreover, L. plantarum L47 and inulin increased the levels of ALA (P < 0.05), lipoteichoic acid (LTA) (P < 0.05), and 12,13-epoxyoctadecenoic acid (12,13-EpOME) (P < 0.05) and the protein expression of Toll-like receptor 2 (TLR2) (P = 0.05) in the ileal mucosa. In conclusion, L. plantarum L47 and inulin together alleviated ETEC-induced ileal inflammation in piglets by up-regulating the levels of ALA and 12,13-EpOME via the LTA/TLR2/PLA2G2A pathway.

ETEC regulates GPR109A expression in intestinal epithelial cells mediated by inflammatory factors secreted by macrophages

Gut microbes control host immunity and homeostasis, and their abnormal changes are associated with the occurrence and development of diseases. GPR109A is an essential receptor on intestinal epithelial cells and interacts with gut microbes. Moreover, increased Enterotoxigenic Escherichia coli K88 strain colonization promotes GPR109A expression in vivo. This study evaluated the detailed mechanism of pathogenic bacteria promoting GPR109A expression. The results revealed that ETEC K88 indirectly fosters GPR109A expression in intestinal epithelial cells by stimulating the production of IL-1β and TNF-α through macrophages which are mediated by ERK1/2 pathway. The study explains the molecular mechanisms by which the bacteria regulate the homeostasis of the host intestinal gene expression during ETEC infection.

Antibacterial Activity of Venom from the Puff Adder (Bitis arietans), Egyptian Cobra (Naja haje), and Red Spitting Cobra (Naja pallida)

Bitis arietans (Puff adder), Naja haje (Egyptian cobra), and Naja pallida (Red spitting cobra) venoms were tested for antimicrobial activity. This evaluation employed disc diffusion and microbroth dilution techniques. Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli, Klebsiella pneumonia, and Salmonella typhi) were used. Aztreonam (30 µg), cefpodoxime (10 µg), cefoxitine (30 µg), streptomycin (25 µg), ceftriaxone (30 µg), nalidixic acid (30 µg), tetracycline (30 µg), and sulfamethoxazole (25 µg) were used as controls. All tests were conducted in triplicate (n = 3). Results. The activity of B. arietans venom against Gram-negative bacteria was significantly lower (p < 0.001) than that of controls. The efficacy of B. arietans venom and sulfamethoxazole against both Gram-positive and Gram-negative bacteria was not significantly different (p > 0.9999). The efficacy of B. arietans venom against Gram-positive bacteria was significantly lower (p < 0.001) than cefoxitin, streptomycin, and tetracycline. The efficacy of N. haje venom against Gram-negative bacteria was significantly lower (p < 0.001) than that of controls. There was no significant difference in the antimicrobial efficacy of N. haje venom and controls against Gram-positive bacteria (p=0.3927 to p=0.9998). There was no significant difference in the efficacy of N. pallida venom and controls against Gram-negative bacteria (p=0.3061 to p=0.9981). There was no significant difference in the efficacy of N. pallida venom and controls against Gram-positive bacteria (p=0.2368 to p > 0.9999). Conclusions. Of all the tested venoms, only Naja pallida venom showed good efficacy against both Gram-positive and Gram-negative bacteria.

A bovine lactoferricin-lactoferrampin-encoding Lactobacillus reuteri CO21 regulates the intestinal mucosal immunity and enhances the protection of piglets against enterotoxigenic Escherichia coli K88 challenge

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in human and animal. To determine the mechanism of a bovine lactoferricin-lactoferrampin (LFCA)-encoding Lactobacillus reuteri CO21 (LR-LFCA) to enhance the intestinal mucosal immunity, we used a newborn piglet intestine model to study the intestinal response to ETEC. Pigs were chosen due to the anatomical similarity between the porcine and the human intestine.4-day-old piglets were orally administered with LR-LFCA, LR-con (L. reuteri CO21 transformed with pPG612 plasmid) or phosphate buffered saline (PBS) for three consecutive days, within 21 days after these treatments, we found that LR-LFCA can colonize the intestines of piglets, improve the growth performance, enhance immune response and is beneficial for intestinal health of piglets by improving intestinal barrier function and modulating the composition of gut microbiota. Twenty-one days after, piglets were infected with ETEC K88 for 5 days, we found that oral administration of LR-LFCA to neonatal piglets attenuated ETEC-induced the weight loss of piglets and diarrhea incidence. LR-LFCA decreased the production of inflammatory factors and oxidative stress in intestinal mucosa of ETEC-infected piglets. Additionally, LR-LFCA increased the expression of tight junction proteins in the ileum of ETEC-infected piglets. Using LPS-induced porcine intestinal epithelial cells (IPEC-J2) in vitro, we demonstrated that LR-LFCA-mediated increases in the tight junction proteins might depend on the MLCK pathway; LR-LFCA might increase the anti-inflammatory ability by inhibiting the NF-κB pathway. We also found that LR-LFCA may enhance the antioxidant capacity of piglets by activating the Nrf2/HO-1 pathway. This study demonstrates that LR-LFCA is effective at maintaining intestinal epithelial integrity and host homeostasis as well as at repairing intestinal damage after ETEC infection and is thus a promising alternative therapeutic method for intestinal inflammation.

Prevalence of Diarrheagenic E. Coli Among Hospitalized Children in a Clinical Centre

Introduction. Escherichia coli is a common cause of acute diarrhea mainly in young children and, less frequently, in elderly or immunosuppressed patients. Many types of E. coli are part of the normal enteric flora, but can cause urinary tract or nervous system infections.

Objective. To study the prevalence of the main types and serogroups of diarrheagenic E. coli among hospitalized children with enteric infections.

Material and methods. Over a period of 5 years, 1,160 hospitalized children with acute diarrhea syndrome were studied. Fecal samples underwent culturing, biochemical and phenotypic identification.

Results. Among the studied patients, 112/1,160 children (9.7%) had diarrhea caused by E. coli, and only 4 of the isolates were lactose-negative. The most common was diarrhea caused by ETEC – 65/112 (58.0%), followed by EPEC – 38/112 (33.9%), and in third place – EHES 9/112 (8.0%). We did not isolate EIEC types. Depending on the group of E. coli, we observed some differences in the clinical presentation and specifics in the distribution of patients by age.

Conclusion. The study shows that this causative agent is common among Bulgarian children with diarrhea. Unfortunately, in Bulgaria the microbiological network is still not able to adequately respond to the challenges of the extended serodiagnosis for detection of diarrheagenic E. coli, which is performed in Western Europe and North America.

Typical and atypical enteropathogenic Escherichia coli in children with acute diarrhoea: Changing trend in East Delhi

Background

Worldwide around 2 million deaths occur every year due to diarrhoeal illnesses among children less than 5 years of age. Among diarrhoeagenic Escherichia coli, Enteropathogenic E. coli (EPEC) is highly prevalent in both community and hospital settings and is one of the main causes of persistent diarrhea in children in developing countries. EPEC remains underdiagnosed in India due to lack of conventional tools for identification.

Methods

We in this study investigated the prevalence and regional variation of EPEC in paediatric population suffering from diarrhoea in East Delhi, India. Two hundred stool samples were collected from children, aged between 0.5 and 5 years, with acute diarrhoea. E. coli were identified by conventional tests and PCR.

Results

We observed 7% atypical EPEC (aEPEC) and 2.5% typical EPEC (tEPEC), with an overall 9.5% EPEC prevalence amongst total samples. E. coli phylogenetic group A was the predominant. The most common age group affected was 6–23 months with common symptoms being vomiting, watery diarrhoea and severe dehydration. High drug resistance pattern was observed in EPEC isolates.

Conclusion

The study depicts a changing trend of aEPEC over tEPEC in children less than 5 years with diarrhoea, an emerging drug resistant enteropathogen and a public health concern demanding monitoring and surveillance.

Spectrum of diarrhoeagenic Escherichia coli in paediatric population suffering from diarrhoea and as commensals in healthy children

BACKGROUND

Diarrhoeagenic Escherichia coli (DEC) is associated with early death of children in developing countries and are being identified now as an important evolving pathogen. The objective of this study was to perform multiplex polymerase chain reaction (PCR) for simultaneous detection of six categories of DEC in two sets of PCR reactions using 11 virulent genes.

MATERIALS AND METHODS

During 1-year study period, forty isolates each from outpatient, inpatient and healthy groups were collected from children. E. coli was identified using conventional biochemical methods. DNA extraction was done using kit, and the extracted DNA was used as a template for multiplex PCR.

RESULTS

Virulent genes of DEC were detected in 106 (88.33%) samples. Overall, elt and est were detected in 8.33% and 30.83% of specimens; typical, atypical enteropathogenic E. coli and bfp were detected in 13.33%, 29.16% and 19.16% specimens; eagg was detected in 39.16% and east in 13.33% specimens and stx and hyla were isolated in 1.66% specimens each. While diffusely adherent E. coli and enteroinvasive E. coli genes were not isolated.

CONCLUSION

Multiplex PCR is a rapid method for the simultaneous detection of 11 virulent genes of DEC at a time and it will provide a platform in understanding the diarrheal diseases in a more improved manner.

Molecular Epidemiology of Extended-Spectrum β-Lactamase-Producing Escherichia coli Pathotypes in Diarrheal Children from Low Socioeconomic Status Communities in Bihar, India: Emergence of the CTX-M Type

Background

Childhood diarrheal diseases remain highly endemic in India, but the emergence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among children with diarrhea in Bihar remains elusive. In this study, we determine and characterize ESBL-producing E coli pathotypes among hospitalized diarrheal preschool children living in low socioeconomic level communities in Bihar, India.

Materials and methods

The stool samples were collected everyday throughout the year for 2 consecutive years. In our study, we collected stool samples randomly from every fifth patient. Stool samples were collected from a total of 633 randomly selected diarrheal children (age: 0-60 months) belonging to 17 communities and screened for identification of virulent diarrheagenic E coli (DEC) pathotype (viz, enteropathogenic E coli [EPEC], enteroaggregative E coli [EAEC], enterotoxigenic E coli [ETEC], enteroinvasive E coli [EIEC], and enterohemorrhagic E coli [EHEC]) by a multiplex polymerase chain reaction (PCR) assay. Furthermore, ESBLs were screened by conventional antibiotic resistance pattern testing and later characterized for the presence of β-lactamase (bla) genes by PCR and DNA sequencing.

Results

Diarrheagenic E coli was detected in 191 cases (30.2%) of the total 633 diarrheic children. Maximum occurrence of DEC was found in ≤12 months age group (72.7%) with prevalence of the EAEC pathotype. Most isolates were resistant to ampicillin, ciprofloxacin, piperacillin, levofloxacin, ceftazidime, cefotaxime, ceftriaxone, and gentamicin, whereas over 96% of them were sensitive to amikacin. About 37.6% of total 191 DEC isolates were ESBL producers (n = 72), being prevalent among ETEC (n = 35; 18.32%), followed by EPEC (n = 21; 10.9%), EAEC (n = 13; 6.8%), and EIEC (n = 3; 1.57%). Interestingly, the commonest β-lactamase was CTX-M type (bla_CTX-M) in 86.1% (n = 62) of the ESBL isolates, followed by bla_SHV (n = 49; 68%), bla_TEM (n = 37; 51.8%), and bla_OXA (n = 21; 29.1%) determinants. Resistance of ESBL isolates was mostly related to ampicillin (100%), ceftriaxone (98.1%), cefotaxime (92.4%), gentamicin (74.1%), and levofloxacin (73.2%), whereas best antimicrobial activities were observed for piperacillin-tazobactam, amikacin, meropenem, and imipenem.

Conclusions

This study revealed that EAEC (72.1%) is the predominant pathotype in Bihar, significantly high in ≤12 months age group children (P = .04). Moreover, the widespread prevalence of ESBLs in children, especially the CTX-M type, is of great concern, which requires monitoring of infection control measures through efficient antimicrobial management and detection of ESBL-producing isolates.

Abundance of Pathogenic Escherichia coli Virulence-Associated Genes in Well and Borehole Water Used for Domestic Purposes in a Peri-Urban Community of South Africa

In the absence of pipe-borne water, many people in Africa, especially in rural communities, depend on alternative water sources such as wells, boreholes and rivers for household and personal hygiene. Poor maintenance and nearby pit latrines, however, lead to microbial pollution of these sources. We evaluated the abundance of Escherichia coli and the prevalence of pathogenic E. coli virulence genes in water from wells, boreholes and a river in a South African peri-urban community. Monthly samples were collected between August 2015 and November 2016. In all, 144 water samples were analysed for E. coli using the Colilert 18 system. Virulence genes (eagg, eaeA, stx1, stx2, flichH7, ST, ipaH, ibeA) were investigated using real-time polymerase chain reaction. Mean E. coli counts ranged between 0 and 443.1 Most Probable Number (MPN)/100 mL of water sample. Overall, 99.3% of samples were positive for at least one virulence gene studied, with flicH7 being the most detected gene (81/140; 57.6%) and the stx2 gene the least detected gene (8/140; 5.7%). Both intestinal and extraintestinal pathogenic E. coli genes were detected. The detection of virulence genes in these water sources suggests the presence of potentially pathogenic E. coli strains and is a public health concern.

The Cytolethal Distending Toxin Contributes to Microbial Virulence and Disease Pathogenesis by Acting As a Tri-Perditious Toxin

This review summarizes the current status and recent advances in our understanding of the role that the cytolethal distending toxin (Cdt) plays as a virulence factor in promoting disease by toxin-producing pathogens. A major focus of this review is on the relationship between structure and function of the individual subunits that comprise the AB₂ Cdt holotoxin. In particular, we concentrate on the molecular mechanisms that characterize this toxin and which account for the ability of Cdt to intoxicate multiple cell types by utilizing a ubiquitous binding partner on the cell membrane. Furthermore, we propose a paradigm shift for the molecular mode of action by which the active Cdt subunit, CdtB, is able to block a key signaling cascade and thereby lead to outcomes based upon programming and the role of the phosphatidylinositol 3-kinase (PI-3K) in a variety of cells. Based upon the collective Cdt literature, we now propose that Cdt is a unique and potent virulence factor capable of acting as a tri-perditious toxin that impairs host defenses by: (1) disrupting epithelial barriers; (2) suppressing acquired immunity; (3) promoting pro-inflammatory responses. Thus, Cdt plays a key role in facilitating the early stages of infection and the later stages of disease progression by contributing to persistence and impairing host elimination.

Occurrence of virulence gene signatures associated with diarrhoeagenic and non-diarrhoeagenic pathovars of Escherichia coli isolates from some selected rivers in South-Western Nigeria

BACKGROUND

Diarrhoeal diseases are attributable to unsafe water stemming from improper sanitation and hygiene and are reportedly responsible for extensive morbidity and mortality particularly among children in developed and developing countries.

METHODS

Water samples from selected rivers in Osun State, South-Western Nigeria were collected and analyzed using standard procedures. Escherichia coli isolates (n=300) were screened for 10 virulence genes using polymerase chain reaction for pathotyping.

RESULTS

While the virulence gene (VG) lt for enterotoxigenic E. coli had the highest prevalence of 45%, the enteropathogenic E. coli genes eae and bfp were detected in 6 and 4% of the isolates respectively. The VGs stx1 and stx2 specific for the enterohemorrhagic E. coli pathotypes were detected in 7 and 1% of the isolates respectively. Also, the VG eagg harboured by enteroaggregative pathotype and diffusely-adherent E. coli VG daaE were detected in 2 and 4% of the isolates respectively and enteroinvasive E. coli VG ipaH was not detected. In addition, the VGs papC for uropathogenic and ibeA for neonatal meningitis were frequently detected in 19 and 3% of isolates respectively.

CONCLUSIONS

These findings reveal the presence of diarrhoeagenic and non-diarrhoeagenic E. coli in the selected rivers and a potential public health risk as the rivers are important resources for domestic, recreational and livelihood usage by their host communities.

Enteropathogenic Escherichia coli Uses NleA to Inhibit NLRP3 Inflammasome Activation

Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are related strains capable of inducing severe gastrointestinal disease. For optimal infection, these pathogens actively modulate cellular functions through the deployment of effector proteins in a type three secretion system (T3SS)-dependent manner. In response to enteric pathogen invasion, the Nod-like receptor pyrin domain containing (NLRP) inflammasome has been increasingly recognized as an important cytoplasmic sensor against microbial infection by activating caspase-1 and releasing IL-1β. EPEC and EHEC are known to elicit inflammasome activation in macrophages and epithelial cells; however, whether the pathogens actively counteract such innate immune responses is unknown. Using a series of compound effector-gene deletion strains of EPEC, we screened and identified NleA, which could subdue host IL-1β secretion. It was found that the reduction is not because of blocked NF-κB activity; instead, the reduction results from inhibited caspase-1 activation by NleA. Immunostaining of human macrophage-like cells following infection revealed limited formation of inflammasome foci with constituents of total caspase-1, ASC and NLRP3 in the presence of NleA. Pulldown of PMA-induced differentiated THP-1 lysate with purified MBP-NleA reveals that NLRP3 is a target of NleA. The interaction was verified by an immunoprecipitation assay and direct interaction assay in which purified MBP-NleA and GST-NLRP3 were used. We further showed that the effector interacts with regions of NLRP3 containing the PYD and LRR domains. Additionally, NleA was found to associate with non-ubiquitinated and ubiquitinated NLRP3 and to interrupt de-ubiquitination of NLRP3, which is a required process for inflammasome activation. Cumulatively, our findings provide the first example of EPEC-mediated suppression of inflammasome activity in which NieA plays a novel role in controlling the host immune response through targeting of NLRP3.

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) cause severe intestinal dysfunction, including watery diarrhea or severe bloody diarrhea, and acute kidney failure (hemolytic uremic syndrome). Transmitted through ingestion of contaminated food, these pathogens colonize and disrupt the linings of intestinal epithelial cells. EPEC and EHEC interrupt many cellular functions, including the inflammation response, to increase their chances of proliferation and survival in the intestine. Upon detection of the invasion, epithelial cells and immune cells secrete inflammatory cytokines to further boost the immune response for efficient clearance of the pathogens. IL-1β is an important inflammatory cytokine, and its secretion is regulated by a multimeric protein complex, termed the inflammasome, in host cells. In this study, we discovered that EPEC injects a bacterial effector protein, NleA, to inhibit the secretion of IL-1β. Exploring the potential mechanisms, we found that NleA does so by directly associating with NLRP3 (Nod-Like Receptor 3), one of the three basic components of the inflammasome, and that the presence of NleA interrupts the de-ubiquitination of NLRP3, which is a prerequisite for the assembly of the inflammasome. As a result, NleA reduces the formation of the NLRP3 inflammasome and negatively regulates the secretion of IL-1β.

[Acute diarrheal disease caused by enteropathogenic Escherichia coli in Colombia]

Intestinal Escherichia coli pathogens are leading causes of acute diarrheal disease in children less than 5 years in Latin America, Africa and Asia and a leading cause of death in children living in poorest communities in Africa and South East Asia. Studies on the role of E. coli pathogens in childhood diarrhea in Colombia and other countries in Latin America are limited due to the lack of detection assays in clinical laboratories at the main urban medical centers. Recent studies report that enterotoxigenic E. coli is the most common E. coli pathogens associated with diarrhea in children less than 5 years of age. Other E. coli pathotypes have been detected in children with diarrhea including enteropathogenic, enteroaggregative, shiga-toxin producing and diffusely adherent E. coli. It was also found that meat and vegetables at retail stores are contaminated with Shiga-toxin producing E. coli and enteroaggregative E. coli, suggesting that food products are involved in transmission and infection of the susceptible host. More studies are necessary to evaluate the mechanisms of transmission, the impact on the epidemiology of diarrheal disease, and management strategies and prevention of these pathogens affecting the pediatric population in Colombia.

Dual priming oligonucleotide (DPO)-based multiplex PCR assay for specific detection of four diarrhoeagenic Escherichia coli in food

In this study, a dual priming oligonucleotide (DPO)-based multiplex PCR assay was developed for the specific detection of four foodborne diarrhoeagenic Escherichia coli (DEC) in food, including enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC) O157:H7 and enteroinvasive E. coli (EIEC). Species-specific DPO primers were designed based on rfbE, LT, ipaH and bfpA genes for EHEC O157:H7, ETEC, EIEC and EPEC respectively. Our optimized DPO-based multiplex PCR assay was able to simultaneously detect these DEC from pure cultures, spiked food or environmental sample with an analytical detection limit of <120 CFU ml(-1) (or g(-1) ) for each at annealing temperature from 45 to 65°C. A total of 336 bacterial strains including 51 target and 285 other bacterial strains were used to evaluate the specificity of the assay, and results showed that specific PCR products were only amplified in strains belonging to target bacteria. Applying the assay to 982 samples collected from food, clinical patients and environmental sources revealed that 73 samples were positive, which were confirmed by conventional culture-based assays combined with serological tests. Taken together, the DPO-based multiplex PCR assay developed in this study is a rapid, specific and reliable tool for efficient screening single or multiple DEC from food in laboratory diagnosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The high specificity of the DPO-based multiplex PCR assay developed in this study without false positive results indicates its great potential to be a rapid, reliable, practical and cost-effective method for the monitoring of diarrhoeagenic E. coli in food.

Molecular Characterization of Enterotoxin-Producing Escherichia coli Collected in 2011-2012, Russia

Enterotoxin-producing Escherichia coli (ETEC) are one of the main causative agents of diarrhea in children especially in developing countries and travel diarrhoea in adults. Pathogenic properties of ETEC associated with their ability to produce a heat-stable (ST) and/or heat-labile (LT) enterotoxins, as well as adhesins providing bacterial adhesion to intestinal epithelial cells. This study presents the molecular characterization of the ETEC isolates collected from the Central and Far-Eastern regions of Russia in 2011–2012. It was shown that all ETEC under study (n=18) had the heat-labile enterotoxin-coding operon elt, and had no the genes of the heat-stable enterotoxin operon est. DNA sequencing revealed two types of nucleotide exchanges in the eltB gene coding subunit B of LT in isolates collected from Cherepovets city (Central region, Russia) and Vladivostok city (Far-East region, Russia). Only one ETEC strain carried genes cfaA, cfaB, cfaC and cfaD coding adhesion factor CFA/I. Expression of LT in four ETEC isolates in the agglutination reaction was detected using a latex test-system. The isolates were assigned to serogroups O142 (n = 6), О6 (n = 4), О25 (n = 5), О26 (n = 2), and O115 (n = 1). Genotyping showed that they belonged to an earlier described sequence-type ST4 (n = 3) as well as to 11 novel sequence-types ST1043, ST1312, ST3697, ST3707, ST3708, ST3709, ST3710, ST3755, ST3756, ST3757 and ST4509. The ETEC isolates displayed different levels of antimicrobial resistance. Eight isolates were resistant to only one drug, three isolates—to two drugs, one isolate—to three drugs, two isolates—to four antibacterials, and only one isolate to each of the five, six and ten antibacterials simultaneously. Genetic determinants of the resistance to beta-lactams and other classes of antibacterials on the ETEC genomes were identified. There are bla_TEM (n = 10), bla_CTX-M-15 (n = 1), class 1 integron (n = 3) carrying resistance cassettes to aminoglycosides and sulphonamides dfrA17-aadA5 and dfrA12-orfF-aadA2. One isolate ETEC_Ef-6 was found to be a multidrug-resistant (MDR) pathogen that carried both the beta-lactamase gene and class 1 integron. These data suggest the circulation of ETEC in Russia. Further investigations are necessary to study the spread of the revealed ETEC sequence types (STs) and serotypes. Their role in the etiology of diarrhea should be also estimated.

Metalloprotease NleC suppresses host NF-κB/inflammatory responses by cleaving p65 and interfering with the p65/RPS3 interaction

Attaching/Effacing (A/E) pathogens including enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC) and the rodent equivalent Citrobacter rodentium are important causative agents of foodborne diseases. Upon infection, a myriad of virulence proteins (effectors) encoded by A/E pathogens are injected through their conserved type III secretion systems (T3SS) into host cells where they interfere with cell signaling cascades, in particular the nuclear factor kappaB (NF-κB) signaling pathway that orchestrates both innate and adaptive immune responses for host defense. Among the T3SS-secreted non-LEE-encoded (Nle) effectors, NleC, a metalloprotease, has been recently elucidated to modulate host NF-κB signaling by cleaving NF-κB Rel subunits. However, it remains elusive how NleC recognizes NF-κB Rel subunits and how the NleC-mediated cleavage impacts on host immune responses in infected cells and animals. In this study, we show that NleC specifically targets p65/RelA through an interaction with a unique N-terminal sequence in p65. NleC cleaves p65 in intestinal epithelial cells, albeit a small percentage of the molecule, to generate the p65¹⁻³⁸ fragment during C. rodentium infection in cultured cells. Moreover, the NleC-mediated p65 cleavage substantially affects the expression of a subset of NF-κB target genes encoding proinflammatory cytokines/chemokines, immune cell infiltration in the colon, and tissue injury in C. rodentium-infected mice. Mechanistically, the NleC cleavage-generated p65¹⁻³⁸ fragment interferes with the interaction between p65 and ribosomal protein S3 (RPS3), a 'specifier' subunit of NF-κB that confers a subset of proinflammatory gene transcription, which amplifies the effect of cleaving only a small percentage of p65 to modulate NF-κB-mediated gene expression. Thus, our results reveal a novel mechanism for A/E pathogens to specifically block NF-κB signaling and inflammatory responses by cleaving a small percentage of p65 and targeting the p65/RPS3 interaction in host cells, thus providing novel insights into the pathogenic mechanisms of foodborne diseases.

A diagnosis of haemolytic-uraemic syndrome blurred by alcohol abuse

A 60-year-old man with a history of alcohol abuse was admitted to the intensive care unit (ICU) for status epilepticus. At first, laboratory and imagery findings were almost normal, and the symptoms were attributed to severe alcohol withdrawal due to a history of gastroenteritis reported by his family. But, during the following days, haemolytic anaemia, thrombocytopenia, acute renal failure, and ischaemic and haemorrhagic lesions seen on a cerebral CT scan led to the diagnosis of haemolytic-uraemic syndrome (HUS). Despite these severe complications, the patient made a good recovery following ICU and plasma exchange with fresh frozen plasma (FFP), but cognitive deficit still existed after 1 month. It is important to know that neurological manifestations can precede typical biological and radiological signs in HUS, and to not be misled in the diagnosis process, especially when a more common differential diagnosis is possible.

Intracellular trafficking of AIP56, an NF-κB-cleaving toxin from Photobacterium damselae subsp. piscicida

AIP56 (apoptosis-inducing protein of 56 kDa) is a metalloprotease AB toxin secreted by Photobacterium damselae subsp. piscicida that acts by cleaving NF-κB. During infection, AIP56 spreads systemically and depletes phagocytes by postapoptotic secondary necrosis, impairing the host phagocytic defense and contributing to the genesis of infection-associated necrotic lesions. Here we show that mouse bone marrow-derived macrophages (mBMDM) intoxicated by AIP56 undergo NF-κB p65 depletion and apoptosis. Similarly to what was reported for sea bass phagocytes, intoxication of mBMDM involves interaction of AIP56 C-terminal region with cell surface components, suggesting the existence of a conserved receptor. Biochemical approaches and confocal microscopy revealed that AIP56 undergoes clathrin-dependent endocytosis, reaches early endosomes, and follows the recycling pathway. Translocation of AIP56 into the cytosol requires endosome acidification, and an acidic pulse triggers translocation of cell surface-bound AIP56 into the cytosol. Accordingly, at acidic pH, AIP56 becomes more hydrophobic, interacting with artificial lipid bilayer membranes. Altogether, these data indicate that AIP56 is a short-trip toxin that reaches the cytosol using an acidic-pH-dependent mechanism, probably from early endosomes. Usually, for short-trip AB toxins, a minor pool reaches the cytosol by translocating from endosomes, whereas the rest is routed to lysosomes for degradation. Here we demonstrate that part of endocytosed AIP56 is recycled back and released extracellularly through a mechanism requiring phosphoinositide 3-kinase (PI3K) activity but independent of endosome acidification. So far, we have been unable to detect biological activity of recycled AIP56, thereby bringing into question its biological relevance as well as the importance of the recycling pathway.

Enhanced protection of pathogenic Escherichia coli ingested by a soil nematode Caenorhabditis elegans against sanitizer treatments

We employed Caenorhabditis elegans as a model to study the effectiveness of sanitizers in killing pathogenic Escherichia coli strains ingested by free-living nematodes. Adult worms that had fed on six pathogenic E. coli strains (highly persistent in the nematode intestine) were treated with three chemical solutions. In planktonic cells, none of the H2O2 and acetic acid treatments influenced the survival of the pathogenic E. coli strains, whereas sodium hypochlorite critically decreased the viability of the strains. Importantly, the survival of the E. coli strains was dramatically increased by persistence in the C. elegans gut under 0.1% sodium hypochlorite, and several strains could survive at a concentration of 0.5%. In addition, all pathogenic E. coli strains in the C. elegans gut survived on the lettuce for 5 days even though they were washed with 0.1% sodium hypochlorite. Taken together, our results indicate that pathogenic E. coli ingested by C. elegans may be protected against washing treatment with commercial sanitizers on raw food materials.

Preponderance of toxigenic Escherichia coli in stool pathogens correlates with toxin detection in accessible drinking-water sources

Since early detection of pathogens and their virulence factors contribute to intervention and control strategies, we assessed the enteropathogens in diarrhoea disease and investigated the link between toxigenic strains of Escherichia coli from stool and drinking-water sources; and determined the expression of toxin genes by antibiotic-resistant E. coli in Lagos, Nigeria. This was compared with isolates from diarrhoeal stool and water from Wisconsin, USA. The new Luminex xTAG GPP (Gastroplex) technique and conventional real-time PCR were used to profile enteric pathogens and E. coli toxin gene isolates, respectively. Results showed the pathogen profile of stool and indicated a relationship between E. coli toxin genes in water and stool from Lagos which was absent in Wisconsin isolates. The Gastroplex technique was efficient for multiple enteric pathogens and toxin gene detection. The co-existence of antibiotic resistance with enteroinvasive E. coli toxin genes suggests an additional prognostic burden on patients.

Role of F1C fimbriae, flagella, and secreted bacterial components in the inhibitory effect of probiotic Escherichia coli Nissle 1917 on atypical enteropathogenic E. coli infection

Enteropathogenic Escherichia coli (EPEC) is recognized as an important intestinal pathogen that frequently causes acute and persistent diarrhea in humans and animals. The use of probiotic bacteria to prevent diarrhea is gaining increasing interest. The probiotic E. coli strain Nissle 1917 (EcN) is known to be effective in the treatment of several gastrointestinal disorders. While both in vitro and in vivo studies have described strong inhibitory effects of EcN on enteropathogenic bacteria, including pathogenic E. coli, the underlying molecular mechanisms remain largely unknown. In this study, we examined the inhibitory effect of EcN on infections of porcine intestinal epithelial cells with atypical enteropathogenic E. coli (aEPEC) with respect to single infection steps, including adhesion, microcolony formation, and the attaching and effacing phenotype. We show that EcN drastically reduced the infection efficiencies of aEPEC by inhibiting bacterial adhesion and growth of microcolonies, but not the attaching and effacing of adherent bacteria. The inhibitory effect correlated with EcN adhesion capacities and was predominantly mediated by F1C fimbriae, but also by H1 flagella, which served as bridges between EcN cells. Furthermore, EcN seemed to interfere with the initial adhesion of aEPEC to host cells by secretion of inhibitory components. These components do not appear to be specific to EcN, but we propose that the strong adhesion capacities enable EcN to secrete sufficient local concentrations of the inhibitory factors. The results of this study are consistent with a mode of action whereby EcN inhibits secretion of virulence-associated proteins of EPEC, but not their expression.

Site-specific immobilization of DNA on silicon surfaces by using the thiol–yne reaction

Covalent immobilization of ssDNA fragments onto silicon-based materials was performed using the thiol–yne reaction.

Structure and mechanism of a type III secretion protease, NleC

NleC is one of the virulence factors that is injected into infected host cells by enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC) via a needle-like protein complex called the type III secretion system (T3SS). The cytosolic NleC specifically cleaves the p65 subunit of NF-κB in the p65-p50 heterodimeric complex just after the Cys38 site in its N-terminal domain. The degradation of the remainder of the p65 C-terminal domain by the proteasome disrupts the NF-κB signalling pathway, thus dampening the host inflammatory response. Here, the crystal structure of NleC is reported at 1.55 Å resolution. In conjunction with biochemical analyses, the structure reveals that NleC is a member of the zincin zinc protease family and that the configuration of the NleC active site resembles that of the metzincin clan of metallopeptidases but without the canonical Met turn of astacin. The extended zinc-binding motif of NleC (HEXXHXXTXXXD) includes three metal ligands. The fifth zinc ligand, a conserved tyrosine (a bound water molecule is the fourth ligand), lies 45 residues downstream of the zincin motif. Furthermore, the electrostatic potential complementarity between NleC and p65 also contributes to the cleavage activity of the protease. These results not only provide important insights into the mechanism of how NleC recognizes its substrates, but also shed light on the design of new antibiotics for the food-borne diseases arising from EPEC and EHEC.

Management strategies in the treatment of neonatal and pediatric gastroenteritis

Acute gastroenteritis, characterized by the onset of diarrhea with or without vomiting, continues to be a major cause of morbidity and mortality in children in mostly resource-constrained nations. Although generally a mild and self-limiting disease, gastroenteritis is one of the most common causes of hospitalization and is associated with a substantial disease burden. Worldwide, up to 40% of children aged less than 5 years with diarrhea are hospitalized with rotavirus. Also, some microorganisms have been found predominantly in resource-constrained nations, including Shigella spp, Vibrio cholerae, and the protozoan infections. Prevention remains essential, and the rotavirus vaccines have demonstrated good safety and efficacy profiles in large clinical trials. Because dehydration is the major complication associated with gastroenteritis, appropriate fluid management (oral or intravenous) is an effective and safe strategy for rehydration. Continuation of breastfeeding is strongly recommended. New treatments such as antiemetics (ondansetron), some antidiarrheal agents (racecadotril), and chemotherapeutic agents are often proposed, but not yet universally recommended. Probiotics, also known as "food supplement," seem to improve intestinal microbial balance, reducing the duration and the severity of acute infectious diarrhea. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition and the European Society of Paediatric Infectious Diseases guidelines make a stronger recommendation for the use of probiotics for the management of acute gastroenteritis, particularly those with documented efficacy such as Lactobacillus rhamnosus GG, Lactobacillus reuteri, and Saccharomyces boulardii. To date, the management of acute gastroenteritis has been based on the option of "doing the least": oral rehydration-solution administration, early refeeding, no testing, no unnecessary drugs.

Update on hemolytic uremic syndrome: Diagnostic and therapeutic recommendations

Hemolytic uremic syndrome (HUS) is a rare disease. In this work the authors review the recent findings on HUS, considering the different etiologic and pathogenetic classifications. New findings in genetics and, in particular, mutations of genes that encode the complement-regulatory proteins have improved our understanding of atypical HUS. Similarly, the complement proteins are clearly involved in all types of thrombotic microangiopathy: typical HUS, atypical HUS and thrombotic thrombocytopenic purpura (TTP). Furthermore, several secondary HUS appear to be related to abnormalities in complement genes in predisposed patients. The authors highlight the therapeutic aspects of this rare disease, examining both "traditional therapy" (including plasma therapy, kidney and kidney-liver transplantation) and "new therapies". The latter include anti-Shiga-toxin antibodies and anti-C5 monoclonal antibody "eculizumab". Eculizumab has been recently launched for the treatment of the atypical HUS, but it appears to be effective in the treatment of typical HUS and in TTP. Future therapies are in phases I and II. They include anti-C5 antibodies, which are more purified, less immunogenic and absorbed orally and, anti-C3 antibodies, which are more powerful, but potentially less safe. Additionally, infusions of recombinant complement-regulatory proteins are a potential future therapy.

Trends in the prevalence of diarrheagenic Escherichia coli among hospitalized diarrheal patients in Kolkata, India

Background

To analyse the trends in the prevalence of different pathogroups of diarrheagenic Escherichia coli (DEC) among hospitalized acute diarrheal patients.

Methodology/Principal Findings

From the active surveillance of diarrheal disease at the Infectious Diseases Hospital, Kolkata, 3826 stool specimens collected during 2008–2011 were screened for DEC and other enteric pathogens. PCR was used in the detection of enterotoxigenic, enteropathogenic and enteroaggregative E. coli and 10 major colonization factor antigens (CFs) of enterotoxigenic E. coli. The relationship between DEC infected patient’s age group and clinical symptoms were also investigated. Multiplex PCR assay showed that the prevalence of EAEC was most common (5.7%) followed by ETEC (4.2%) and EPEC (1.8%). In diarrheal children >2 year of age, EAEC and EPEC were detected significantly (p = 0.000 and 0.007, respectively). In children >2 to 5 and >5 to 14 years, ETEC was significantly associated with diarrhea (p = 0.000 each). EAEC was significantly associated with diarrheal patients with age groups >14 to 30 and >30 to 50 years (p = 0.001, and p = 0.009, respectively). Clinical symptoms such as vomiting, abdominal pain, watery diarrhea, were recorded in patients infected with ETEC. Dehydration status was severe among patients infected by ST-ETEC (19%) and EPEC (15%). CS6 was frequently detected (37%) among ETEC.

Conclusions/Significance

Hospital based surveillance reviled that specific pathogroups of DEC are important to certain age groups and among ETEC, CS6 was predominant.

The enterohemorrhagic Escherichia coli effector protein NleF binds mammalian Tmp21

The human pathogens enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC), as well as the mouse pathogen Citrobacter rodentium encode type III secretion system (T3SS) effector proteins to promote their survival in the infected host. The mechanisms of action and the host targets of T3SS effectors are under active investigation because of their importance to bacterial virulence. The non-locus of enterocyte effacement (LEE)-encoded protein F, NleF, contributes to E. coli and C. rodentium colonization of piglets and mice, respectively. Here we sought to characterize the host binding partners of NleF. Using a yeast two-hybrid screen, we identified Tmp21, a type-I integral membrane protein and COPI-vesicle receptor involved in trans-Golgi network function, as an NleF-binding partner. We confirmed this interaction using immunoprecipitation and bimolecular fluorescence complementation (BiFC). We expressed a temperature-sensitive vesicular stomatitis virus glycoprotein (tsVSVG) to monitor protein trafficking and determined that NleF slows the intracellular trafficking of tsVSVG from the endoplasmic reticulum to the Golgi.

Targeting aminopeptidase N, a newly identified receptor for F4ac fimbriae, enhances the intestinal mucosal immune response

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea in human and animal. In piglets, ETEC having F4 fimbriae (F4(+) ETEC) induce severe diarrhea, dependent on the presence of receptors for F4 (F4R). In this study, porcine aminopeptidase N (pAPN) was identified as an F4R by comparative proteomic analysis of brush border proteins of F4R(+) and F4R(-) pigs and by adherence/internalization experiments on pAPN-transfected cells. Binding of F4 fimbriae to pAPN depended on sialic acid containing carbohydrate moieties, and resulted in clathrin-mediated endocytosis of the fimbriae. Endocytosis via pAPN was not restricted to F4 fimbriae, but was also observed for anti-pAPN antibodies. Both F4 fimbriae- and pAPN-specific antibodies were taken up in vivo by porcine enterocytes and induced subsequently a rapid immunoglobulin A and G response. In conclusion, we identified pAPN as an endocytotic receptor for F4 fimbriae and highlight the opportunity to target vaccine antigens to this epithelial receptor.

Enteroaggregative Escherichia coli pathotype: a genetically heterogeneous emerging foodborne enteropathogen

Until now, a common feature that defines the enteroaggregative Escherichia coli (EAEC) strains is the ability to produce a 'stacked-brick' appearance on epithelial cells, but it does not distinguish between pathogenic and nonpathogenic strains. Numerous adhesins, toxins, and proteins associated with virulence have been described, as well as multiple factors contributing to EAEC-induced inflammation. None of these factors are found in all EAEC isolates, and no single factor has ever been implicated in EAEC virulence. The European outbreak of Shiga-toxin-producing EAEC raises its pathogenic potential and interest on finding the true pathogenic factors that may define this pathotype. EAEC were first associated with persistent diarrhea in infants from developing countries, since then they have increasingly been linked as a cause of acute and persistent diarrhea in young infants and children in developing and industrialized countries, individuals infected with human immunodeficiency virus, as a cause of acute diarrhea in travelers from industrialized regions, and with foodborne outbreaks. A major effect of EAEC infection is on the malnourished children in developing countries. Here, we will discuss the EAEC public health relevance and their complexity because of the strain heterogeneity regarding their pathogenesis, identification, diagnosis, lineage, epidemiology, and clinical manifestations.

Epidemiology of Shiga toxin producing Escherichia coli in Australia, 2000-2010

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) are an important cause of gastroenteritis in Australia and worldwide and can also result in serious sequelae such as haemolytic uraemic syndrome (HUS). In this paper we describe the epidemiology of STEC in Australia using the latest available data.

METHODS

National and state notifications data, as well as data on serotypes, hospitalizations, mortality and outbreaks were examined.

RESULTS

For the 11 year period 2000 to 2010, the overall annual Australian rate of all notified STEC illness was 0.4 cases per 100,000 per year. In total, there were 822 STEC infections notified in Australia over this period, with a low of 1 notification in the Australian Capital Territory (corresponding to a rate of 0.03 cases per 100,000/year) and a high of 413 notifications in South Australia (corresponding to a rate of 2.4 cases per 100,000/year), the state with the most comprehensive surveillance for STEC infection in the country. Nationally, 71.2% (504/708) of STEC infections underwent serotype testing between 2001 and 2009, and of these, 58.0% (225/388) were found to be O157 strains, with O111 (13.7%) and O26 (11.1%) strains also commonly associated with STEC infections. The notification rate for STEC O157 infections Australia wide between 2001-2009 was 0.12 cases per 100,000 per year. Over the same 9 year period there were 11 outbreaks caused by STEC, with these outbreaks generally being small in size and caused by a variety of serogroups. The overall annual rate of notified HUS in Australia between 2000 and 2010 was 0.07 cases per 100,000 per year. Both STEC infections and HUS cases showed a similar seasonal distribution, with a larger proportion of reported cases occurring in the summer months of December to February.

CONCLUSIONS

STEC infections in Australia have remained fairly steady over the past 11 years. Overall, the incidence and burden of disease due to STEC and HUS in Australia appears comparable or lower than similar developed countries.

A self-heating cartridge for molecular diagnostics

A disposable, water-activated, self-heating, easy-to-use, polymeric cartridge for isothermal nucleic acid amplification and visual fluorescent detection of the amplification products is described. The device is self-contained and does not require any special instruments to operate. The cartridge integrates chemical, water-triggered, exothermic heating with temperature regulation facilitated with a phase-change material (PCM) and isothermal nucleic acid amplification. The water flows into the exothermic reactor by wicking through a porous paper. The porous paper's characteristics control the rate of water supply, which in turn controls the rate of exothermic reaction. The PCM material enables the cartridge to maintain a desired temperature independent of ambient temperatures in the range between 20 °C and 40 °C. The utility of the cartridge is demonstrated by amplifying and detecting Escherichia coli DNA with loop mediated isothermal amplification (LAMP). The device can detect consistently as few as 10 target molecules in the sample. With proper modifications, the cartridge also can work with other isothermal nucleic acid amplification technologies for detecting nucleic acids associated with various pathogens borne in blood, saliva, urine, and other body fluids as well as in water and food. The device is suitable for use at home, in the field, and in poor-resource settings, where access to sophisticated laboratories is impractical, unaffordable, or nonexistent.

Occurrence of diarrheagenic Escherichia coli genes in raw water of water treatment plants

PURPOSE

The high incidences of waterborne diseases are frequently associated with diarrheagenic Escherichia coli (DEC). DEC may pose a health risk to people who contact surface water for recreation or domestic use. However, there is no published report on the monitoring of DEC in drinking water sources in Taiwan. In this study, the occurrence of DEC genes in raw water for water treatment plants in Taiwan was investigated.

METHOD

Raw water samples were taken from water treatment plants adjacent to the Kaoping River in southern Taiwan. Each water sample was treated with membrane filtration followed by DNA extraction from the concentrate and concentrate enrichment, respectively. The target genes for various DEC strains of genes were identified, including enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC).

RESULTS

Among 55 water samples analyzed, DEC genes were detected in 16 (29.1%) samples. Strain-specific genes for EAEC, EHEC, EIEC, and EPEC were found in the percentages of 3.6%, 10.9%, 9.1%, and 9.1%, respectively. The specific gene for ETEC is not detected in the study. By looking at the presence/absence of specific genes and water sample characteristics, water temperature was found to differ significantly between samples with and without EHEC gene. In addition, pH levels differed significantly for EHEC and EPEC presence/absence genes, and turbidity was significantly different for water with and without EPEC genes.

CONCLUSION

DEC genes were detected in 29.1% of the raw water samples in the study location. The potential health threat may be increased if the treatment efficiencies are not properly maintained. Routine monitoring of DEC in drinking water sources should be considered.

A disposable, integrated loop-mediated isothermal amplification cassette with thermally actuated valves

An inexpensive, disposable, integrated, polymer-based cassette for loop-mediated isothermal amplification (LAMP) of target nucleic acids was designed, fabricated, and tested. The LAMP chamber was equipped with single-use, thermally actuated valves made with a composite consisting of a mixture of PDMS and expandable microspheres. The effect of the composite composition on its expansion was investigated, and the valve's performance was evaluated. In its closed state, the valve can hold pressures as high as 200 kPa without any significant leakage. Both the LAMP chamber and the valves were actuated with thin film heaters. The utility of the cassette was demonstrated by carrying out LAMP of Escherichia coli DNA target and reverse transcribed loop meditated isothermal amplification (RT-LAMP) of RNA targets. The amplicons were detected in real time with a portable, compact detector. The system was capable of detecting as few as 10 target molecules per sample in well under 1 h. The portable, integrated cassette system described here is particularly suited for applications at the point of care and in resource-poor countries, where funds and trained personnel are in short supply.

NleC, a type III secretion protease, compromises NF-κB activation by targeting p65/RelA

The NF-κB signaling pathway is central to the innate and adaptive immune responses. Upon their detection of pathogen-associated molecular patterns, Toll-like receptors on the cell surface initiate signal transduction and activate the NF-κB pathway, leading to the production of a wide array of inflammatory cytokines, in attempt to eradicate the invaders. As a countermeasure, pathogens have evolved ways to subvert and manipulate this system to their advantage. Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are closely related bacteria responsible for major food-borne diseases worldwide. Via a needle-like protein complex called the type three secretion system (T3SS), these pathogens deliver virulence factors directly to host cells and modify cellular functions, including by suppressing the inflammatory response. Using gain- and loss-of-function screenings, we identified two bacterial effectors, NleC and NleE, that down-regulate the NF-κB signal upon being injected into a host cell via the T3SS. A recent report showed that NleE inhibits NF-κB activation, although an NleE-deficient pathogen was still immune-suppressive, indicating that other anti-inflammatory effectors are involved. In agreement, our present results showed that NleC was also required to inhibit inflammation. We found that NleC is a zinc protease that disrupts NF-κB activation by the direct cleavage of NF-κB's p65 subunit in the cytoplasm, thereby decreasing the available p65 and reducing the total nuclear entry of active p65. More importantly, we showed that a mutant EPEC/EHEC lacking both NleC and NleE (ΔnleC ΔnleE) caused greater inflammatory response than bacteria carrying ΔnleC or ΔnleE alone. This effect was similar to that of a T3SS-defective mutant. In conclusion, we found that NleC is an anti-inflammatory bacterial zinc protease, and that the cooperative function of NleE and NleC disrupts the NF-κB pathway and accounts for most of the immune suppression caused by EHEC/EPEC.

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) cause food-borne diseases, including watery diarrhea or severe bloody diarrhea and life-threatening kidney disease (hemolytic uremic syndrome). Upon ingestion, EPEC/EHEC colonize the cells of the epithelial lining in the intestinal tract. In response, the affected cells initiate an immune response by secreting cytokines that attract immune cells. To prevent their early elimination by the host, these bacteria have developed strategies to prevent the host immune response. They do this by injecting bacterial effectors into the host cells to disrupt the NF-κB pathway, an essential effector of the host cell immune response. In the current study, we report the discovery of an NF-κB suppressive effector in EPEC/EHEC called NleC, and its novel mechanism. We found that NleC is a zinc protease that can digest p65, a critical component of the NF-κB pathway, thus dampening the host inflammatory response. NleE is another recently identified anti-inflammatory effector. We show here that an EPEC/EHEC mutant deficient in both NleC and NleE loses most of its ability to suppress the host inflammatory response. Our findings show how two different bacterial effectors can function in cooperation to modify the host immune response.

Distribution of Virulence Genes and Their Association of Serotypes in Pathogenic Escherichia coli Isolates From Diarrheal Patients in Korea

Objectives

To characterise the genetic and serological diversity of pathogenic Escherichia coli, we tested 111 E coli strains isolated from diarrhoeal patients in Korea between 2003 and 2006.

Methods

The isolates were tested through polymerase chain reaction (PCR) and slide agglutination method for the detection of virulence genes and serotypes, respectively. To compare the expression of Shiga toxin (stx)-1 and stx2 genes, real-time quantitative reverse-transcriptase PCR and rapid exprssion assay, reversed-passive latex agglutination, were performed.

Results

Forty-nine Shiga toxin-producing E coli (STEC) strains and 62 non-STEC strains, including 20 enteropathogenic E coli, 20 enterotoxigenic E coli, 20 enteroaggregative E coli, and 2 enteroinvasive E coli were randomly chosen from the strains isolated from diarrhoeal patients in Korea between 2003 and 2006. PCR analysis indicated that locus of enterocyte effacement pathogenicity island, that is, eaeA, espADB, and tir genes were present in STEC, enteropathogenic E coli, and enteroinvasive E coli. Quorum sensing-related gene luxS was detected in most of pathogenic E coli strains. Major serotypes of the STEC strains were O157 (26%) and O26 (20%), whereas the non-STEC strains possessed various serotypes. Especially, all the strains with serotype O157 carried stx2 and the tested virulence factors. Of the STEC strains, the data of real-time quantitative reverse-transcriptase PCR and reversed-passive latex agglutination tests showed that messenger RNA- and protein expression of stx2 gene were higher than those of stx1 gene.

Conclusion

Our results provide the epidemiological information regarding the trend of STEC and non-STEC infections in the general population and show the fundamental data in association of serotypes with virulence genes in diarrhoeagenic E coli strains from Korea.

Enterotoxigenic Escherichia coli (K88) induce proinflammatory responses in porcine intestinal epithelial cells

Infections with F4(+) enterotoxigenic Escherichia coli (ETEC) causes severe diarrhoea in piglets, resulting in morbidity and mortality. F4 fimbriae are the key virulence factors mediating the attachment of F4(+) ETEC to the intestinal epithelium. Intestinal epithelial cells (IEC) are recently being recognized as important regulators of the intestinal immune system through the secretion of cytokines, however, data on how F4(+) ETEC affect this cytokine secretion are scarce. By using ETEC strains expressing either polymeric, monomeric or F4 fimbriae with a reduced polymeric stability, we demonstrated that polymeric fimbriae are essential for adhesion to porcine IEC and the secretion of IL-6 and IL-8 by IEC. Remarkably, this cytokine secretion was not abrogated following stimulation with an F4-negative strain. Since this strain expresses flagellin, TLR5 mediated signalling could be involved. Indeed, porcine IEC express TLR5 and purified flagellin induced IL-6 and IL-8 secretion, indicating that, as for other pathogens, flagellin is the dominant virulence factor involved in the induction of proinflammatory responses in IEC. These results indicate a potential mucosal adjuvant capacity of ETEC-derived flagellin and may improve rational vaccine design against F4(+) ETEC infections.

Review article: rifaximin, a minimally absorbed oral antibacterial, for the treatment of travellers' diarrhoea

BACKGROUND

Travellers' diarrhoea, a common problem worldwide with significant medical impact, is generally treated with anti-diarrhoeal agents and fluid replacement. Systemic antibiotics are also used in selected cases, but these may be associated with adverse effects, bacterial resistance and drug-drug interactions.

AIM

To review the clinical evidence supporting the efficacy and safety of the minimally absorbed oral antibiotic rifaximin in travellers' diarrhoea.

METHODS

PubMed and the Cochrane Register of Controlled Clinical Trials (to January 2010) and International Society of Travel Medicine congress abstracts (2003-2009) were searched to identify relevant publications.

RESULTS

A total of 10 publications were included in the analysis. When administered three times daily for 3 days, rifaximin is superior to placebo or loperamide; it is at least as effective as ciprofloxacin in reducing duration of illness and restoring wellbeing in patients with travellers' diarrhoea, both with and without identification of a pathogen, as well as in diarrhoea caused by Escherichia coli infection. Rifaximin demonstrates only minimal potential for development of bacterial resistance and for cytochrome P450-mediated drug-drug interactions, and its tolerability profile is similar to that of placebo.

CONCLUSION

When antibiotic therapy is warranted in uncomplicated travellers' diarrhoea, rifaximin may be considered as a first-line treatment option because of its favourable efficacy, tolerability and safety profiles.

Isolation of a bacteriophage specific for CS7-expressing strains of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of childhood diarrhoea in Bangladesh. Among the virulence factors of ETEC, toxins and colonization factors (CFs) play a major role in pathogenesis. Unlike Vibrio cholerae, the relationship between ETEC and ETEC-specific phages is poorly understood and the possible role of ETEC phages in the evolution of ETEC strains in the environment is yet to be established. This study was designed specifically to isolate phages that are specific for ETEC virulence factors. Among the 49 phages isolated from 12 different surface water samples, 13 were tested against 211 ETEC strains collected from clinical and environmental sources. One phage, designated IMM-001, showed a significant specificity towards CS7 CF as it attacked all the CS7-expressing ETEC. Electron microscopic analyses showed that the isolated phage possessed an isomeric hexagonal head and a long filamentous tail. An antibody blocking method and phage neutralization assay confirmed that CS7 pilus is required for the phage infection process, indicating the role of CS7 fimbrial protein as a potential receptor for IMM-001. In summary, this study showed the presence of a lytic phage in environmental water that is specific for the CS7 CF of ETEC.